GLOSSAET. 289 



third of a revolution, thus making a regular aud uniform application of 

 the force. 



Cross-cut Saw, a large saw Avorkcd by a man at each end, for cutting 

 logs. 



Cutter-bar, the cutthig apparatus of a mowing or reaping machine. 



Cycloid, a curve made by any point in a circle rolling on a straight 

 line, and marking the curve on a plane surfoce at the side of the circle. 

 A rail driven in the rim of a wagon- wheel, driven through a snow bank, 

 will mark a cycloid on the snow. An epicycloid is made by a similar 

 revolution of a circle, rolling on the circumference of another circle, 

 externally or interually. 



Dead centre, a centre which does not revolve. 



Dead furrow, the furroAV where the plow throws the earth in oppo- 

 site directions, or where the furrows meet in plowing a strip of land. 



Derrick, a pole or upright timber for supporting a crane, used in lift- 

 ing heavy materials in building and for other purposes. 



Dog, an iron catch or clutch, driven into the end of a saw-log, to hold 

 it in a fixed position while sawing. 



Double-tree, the central whiffle-tree of a two-horse set. 



Dowel, a short iron or wooden pin to join two pieces of timber, pro- 

 tecting from one timber into a hole in the corresponding one. A 

 familiar example occurs in the manner in which a cooper secures two or 

 more boards in forming the head of a cask. 



Draught, Aijgle of, the angle made by a line of draught with a line 

 drawn on ,he surface over which the body is drawn. 



Dredge, or Dredging Machine, a machine for scooping up mud or 

 earth from under water, for clearing the channels of canals, rivers, and 

 harbors. 



Drill, a furrow for the reception of seed, or a row of growing plants ; 

 also a machine for sowing seed in continuous rows. 



Driving-wheel, the wheel of a mowing or reaping machine, which 

 runs on the ground, and propels the gearing. 



Drum, a revolving cylinder, around which belts or endless straps are 

 passed, to communicate motion. 



Dynamics, the science of motion and forces. 



Dynamometer, an instrument for measuring forces, applied to plows, 

 mowing machines, thrashing machines, etc., to show the amount of 

 force required to work them. 



Eccentric, out of centre ; applied to wheels, discs, or circles, with 

 the axle out of centre, to create reciprocating motion. Ikcentric rod is 

 the rod that transmits the motion of the eccentric wheel. 



Elevator, an endless revolving leather strap, set with sheet-iron 

 boxes or cups, for raising grain. The term is also applied to buildings 

 into which grain is thus elevated and stored. 



Emery wheel, a Avheel set with emery at the circumference, for 

 grinding or polishing metals. 



Endless chain, a chain with the ends connected together, rui^ning on 

 13 



